ENSO statistics, teleconnections, and atmosphere-ocean coupling in theTaiwan Earth System Model version 1

This study provides an overview of the fundamentalstatistics and features of the El Nino-Southern Oscillation (ENSO) inthe historical simulations of the Taiwan Earth System Model version 1(TaiESM1). Compared with observations, TaiESM1 can reproduce the fundamentalfeatures of observed ENSO signals, including seasonal phasing, thermoclinecoupling with winds, and atmospheric teleconnection during El Ninoevents. However, its ENSO response is approximately 2 times stronger thanobserved in the spectrum, resulting in powerful teleconnectionsignals. The composite of El Nino events shows a strong westerly anomalyextending fast to the eastern Pacific in the initial stage in March, April, andMay, initiating a warm sea surface temperature anomaly (SSTA) there. Thiswarm SSTA is maintained through September, October, and November (SON) andgradually diminishes after peaking in December. Analysis of wind stress-SSTand heat flux-SST coupling indicates that biased positive SST-shortwavefeedback significantly contributes to the strong warm anomaly over theeastern Pacific, especially in SON. Our analysis demonstrates TaiESM1'scapability to simulate ENSO - a significant tropical climate variation oninterannual scales with strong global impacts - and provides insights intomechanisms in TaiESM1 related to ENSO biases, laying the foundation forfuture model development to reduce uncertainties in TaiESM1 and climatemodels in general.